As a head mounted display has been lightened, users can wear the head mounted display like glasses. Users can perform a voice call or a video call using the head mounted display. Since it is difficult for the head mounted display to be equipped with various buttons on the surface of the head mounted display, the head mounted display may have low operability due to an attribute of the device. Hence, in case of performing a voice call or a video call using the head mounted display, a method of providing an additional function via a simple operation is required. For instance, in case of performing a voice call or a video call, a method of controlling the head mounted display not to deliver a voice of a user to the other party with a simple operation only is required.